DESCRIPTION

Perl debug information is frequently required not just by debuggers,
but also by modules that need some "special" information to do their
job properly, like profilers.

This module abstracts and provides all of the hooks into Perl internal
debugging functionality, so that various implementations of Perl debuggers
(or packages that want to simply get at the "privileged" debugging data)
can all benefit from the development of this common code. Currently used
by Swat, the perl/Tk GUI debugger.

Note that multiple "front-ends" can latch into this debugging API
simultaneously. This is intended to facilitate things like
debugging with a command line and GUI at the same time, debugging
debuggers etc. [Sounds nice, but this needs some serious support -- GSAR]

In particular, this API does not provide the following functions:

data display

command processing

command alias management

user interface (tty or graphical)

These are intended to be services performed by the clients of this API.

This module attempts to be squeaky clean w.r.t usestrict;
and when
warnings are enabled.

Global Variables

The following "public" global names can be read by clients of this API.
Beware that these should be considered "readonly".

$DB::sub

Name of current executing subroutine.

%DB::sub

The keys of this hash are the names of all the known subroutines. Each value
is an encoded string that has the sprintf(3) format
("%s:%d-%d",filename,fromline,toline)
.

$DB::single

Single-step flag. Will be true if the API will stop at the next statement.

$DB::signal

Signal flag. Will be set to a true value if a signal was caught. Clients may
check for this flag to abort time-consuming operations.

$DB::trace

This flag is set to true if the API is tracing through subroutine calls.

@DB::args

Contains the arguments of current subroutine, or the @ARGV
array if in the
toplevel context.

@DB::dbline

List of lines in currently loaded file.

%DB::dbline

Actions in current file (keys are line numbers). The values are strings that
have the sprintf(3) format ("%s\000%s",breakcondition,actioncode)
.

$DB::package

Package namespace of currently executing code.

$DB::filename

Currently loaded filename.

$DB::subname

Fully qualified name of currently executing subroutine.

$DB::lineno

Line number that will be executed next.

API Methods

The following are methods in the DB base class. A client must
access these methods by inheritance (*not* by calling them directly),
since the API keeps track of clients through the inheritance
mechanism.

CLIENT->register()

register a client object/package

CLIENT->evalcode(STRING)

eval STRING in executing code context

CLIENT->skippkg('D::hide')

ask DB not to stop in these packages

CLIENT->run()

run some more (until a breakpt is reached)

CLIENT->step()

single step

CLIENT->next()

step over

CLIENT->done()

de-register from the debugging API

Client Callback Methods

The following "virtual" methods can be defined by the client. They will
be called by the API at appropriate points. Note that unless specified
otherwise, the debug API only defines empty, non-functional default versions
of these methods.

CLIENT->init()

Called after debug API inits itself.

CLIENT->prestop([STRING])

Usually inherited from DB package. If no arguments are passed,
returns the prestop action string.

CLIENT->stop()

Called when execution stops (w/ args file, line).

CLIENT->idle()

Called while stopped (can be a client event loop).

CLIENT->poststop([STRING])

Usually inherited from DB package. If no arguments are passed,
returns the poststop action string.

CLIENT->evalcode(STRING)

Usually inherited from DB package. Ask for a STRING to be eval-ed
in executing code context.

CLIENT->cleanup()

Called just before exit.

CLIENT->output(LIST)

Called when API must show a message (warnings, errors etc.).

BUGS

The interface defined by this module is missing some of the later additions
to perl's debugging functionality. As such, this interface should be considered
highly experimental and subject to change.

AUTHOR

Gurusamy Sarathy gsar@activestate.com

This code heavily adapted from an early version of perl5db.pl attributable
to Larry Wall and the Perl Porters.